Catalytic dealkylation of alkyl aromatics



CATALYTIC DEALKYLATION OF ARDMATICS Paul M. Pitts, In, Media, and William K. Griesinger, Haverford,. Pa., assignors to The Atlantic Refining Company, Philadelphia, Pa., a corporation of Pennsylvania ALKYL No Drawing. Application February 28, 1957 Serial No. 642,951

Claims. (Cl. 260-672) States Patent R 2,931,842 Patented Apr, 5, 1960 Heretofore, various expedients were employed to utilize the undesired alkylate fractions, however, generally they were utilized as fuel rather than as chemical compounds and consequently this loss was reflected in the cost of the final detergent. According to the instant invention the costly aromatic portion of alkylated aromatic hydrocarbons may be recovered in the pure form with high yields, while the alkyl portion may likewise be recovered in pure form. Obviously, the aromatics thus produced may be recycled to the alkylation reaction and thus lower the final cost of the detergent. The alkyl groups which are removed are largely isoparafiinic in structure and consequently are very valuable as high octane gasoline blending components. In addition, if the side chains are quite long, cracking of these long chains will occur during the dealkylation reaction thus l producing smaller branched-chain fragments extremely tion-and market forecasts indicate increased consump tion will continue for many years to come. The alkyl aryl sulfonates are probably the most important type of these materials from many standpoints. While there are several methods of producing alkyl aryl sulfonates presently being employed commercially, one method which has found particular favor among petroleum refining companies involves the use of certain light hydrocarbons which otherwise' would have only fuel value. In this method three carbon or four carbon olefins are polymerized, generally by' H PO or BF catalysts, to the trimer, tetramer or pentarner stages for the three carbon olefins and the dimer or trimer stages'for the four carbon olefins. These higher olefins are then used to alkylate benzene or naphthalene to produce the corresponding alkylated benzene or alkylated naphthalene hydrocarbons. The alkylation reaction is also promoted by a catalyst, generally of the Friedel-Crafts type,'such as AlCl BF etc. Finally, the alkylated aromatic hydrocarbons are sulfonated by well known methods to produce the corresponding sulfonic acids which may be neutralized by a variety of basic materials to 'form the corresponding sulfonates, the most important being the sodium salts of the sulfonic acids While these methods of synthesis have been studied in great detail in order to produce extremely pure products of narrow molecular weight range, it has not been possible to eliminate completely the production of some lay-products. The'most useful alkyl aryl sulfon'ates are the alkylated benzene sulfonates in which the alkyl group contains from 9 to 15 carbon atoms, with the trend being in the range of from 12 to 15 carbon atoms. The first step which. involves the catalytic polymerization of propylene will produce polymers both above and below the desired C to C range. Thus, there will be produced some dimers (C some trimers (C and some hexarners (C and higher hydrocarbons. Also because of chain splitting there will be produced intermediates having 7, 8, 10, 11, etc., carbon atoms. Even with the most careful fractional distillation a considerable amount of these hydrocarbons willremain in the C to C 5 fraction. alkylate the aromatic hydrocarbons, undesired alkylated aromatics, i.e. those outside of the desired range, also will be produced. Furthermore, additional undesired alkylated aromatics will be produced, some with as few as three carbon atoms in the side chain, since during alkylation there are appreciable degradation reactions os ur a- Thus, when this desired fraction is used to useful as high octane gasoline components.

' Although specific reference has been made to the dealkylation of undesired alkylated aromatics produced during the synthesis of alkyl aryl sulfonates, which materials are usually the monoalkylated aromatics, the catalytic process of this invention is equally applicable to the dealkylation of both monoand poly-alkylated benzenes or monoor poly-alkylated naphthalenes from any source whatsoever provided that all such alkyl groups to be removed contain at least three carbon atoms.- In this connection it should be pointed out that if the alkylated aromatic contains more than one alkyl group, only those groups which have three or more carbon atoms will be removed by the process of the instant invention.

Uncontrolled dealkylation of aromatic hydrocarbons has been practiced heretofore simply by passing such alkylated aromatics over a cracking catalyst, such as over a silica-alumina cracking catalyst, either alone or in ad: mixture with other hydrocarbons such as a catalytic cracking feed stock used in the production of gasoline. In such cracking processes alkyl groups will be removed, or at least a portion thereof will be removed from the aromatic hydrocarbon nucleus, however, such catalysts also will crack at least a portion of the resulting hydrocarbons into coke and thus the yield of valuable products is markedly decreased. In the method of the instant invention coking is almost completely avoided with the result that the dealkylation produces extremely high yields of pure hydrocarbons.

This invention is also distinguished from non-catalytic dealkylation processes which require extremely high temperatures and pressures.

- It is an object of this invention to provide a catalytic method of dealkylating alkylated benzene hydrocarbons andalkylated naphthalene hydrocarbons, wherein the alkyl groups contain at least 3 carbon atoms. h It is a further object of this invention to provide a catalytic method of dealkylating alkylated benzene hydrocarbons and alkylated naphthalene hydrocarbons to produce pure benzene and pure naphthalene.

It is a further object of this invention to provide a catalytic method of dealkylating alkylated benzene hydroc rbons and alkylated naphthalene hydrocarbons to produce isop rafiinic hydrocarbons.

It is a further obiect of this invention to catalvti ally dealkvlate alkvlated benzene hydrocarbons and alkylated naphthalene hvdrocarbons wherein the alkyl groups contain at least three carbon atoms with high yields of benzene and naphthalene andminimum coke production.

Other objects of this invention will be apparent from the detailed description and appended claims which follow.

In accordance with the instant invention the alkylated aromatic hydrocarbon charge together with excess hydrogen is passed at an elevated temperature and pressure over a catalyst which contains as the active components an acidic metal oxide and platinum. The amount of hydrogen may range between one mole and 20 moles per mole of hydrocarbon based on the average molecular weight of the hydrocarbon charge. Since theoretically one mole of hydrogen will be consumed for each mole of hydrocarbon dealkylated and since hydrogen is required to keep the catalyst active and free of coke it is preferred that the lower limit be about 3 mols of hydrogen per mole of hydrocarbon charge. Moreover, since a large excess of hydrogen beyond that required for the aforementioned uses does not particularly benefit the process, but instead increases processing costs, amounts below about 15 mols per mole of hydrocarbon are preferred.

Temperatures required for the desired reaction range between 600 F. and 1000 F. at pressures of from 50 to 750 pounds per square inch. The preferred reaction conditions are temperatures between 750 F. and 950 F. and pressures between 100 and 500 pounds per square inch. Temperatures are chosen with regard to proper reaction promotion without catalyst deactivation and the pressures are chosen with the object of keeping the aro matic rings intact without hydrogenation.

Since the dealkylation reaction is extremely rapid, space velocities in volumes of liquid charge per volume of catalyst per hour may range between 0.5 and 20 with from 1 to 10 preferred. 7

As has been pointed out, the invention is applicable to monoor poly-alkylated benzenes or monoor polyalkylated naphthalenes provided the alkyl groups which are to be removed contain at least three carbon atoms. Although if an alkylated compound such as ethyl benzene is treated by this process some dealkylation will occur, the yield is not sufiiciently high to be encompassed by the primary objects of the invention which are to produce the pure aromatic in high yield. If a compound such as propy] toluene is treated by the process of the invention the propyl group will be removed leaving .toluene. Thus the invention is applicable to propyl, butyl, or higher alkylated benzenes both monoand polyand the corresponding alkylated naphthalenes. The higher alkylated compounds such as those produced by the alkylation of benzene with chlorinated higher paraffins can also be treated. The upper limit of compounds which may be treated by this invention are those which cannot be vaporized at the reaction conditions employed, since the process is a vapor phase reaction. Compounds which have halogen, hydroxyl or other hetero-containing groups substituted either on the ring or on the side chain likewise may be treated to produce the pure aromatic provided the side chains also contain three carbon atoms.

The catalyst most useful for promoting the reactions of the instant invention consists essentially of an active acidic metal oxide component and platinum. The active acidic metal oxide component is preferably silica-alumina, however, silica-magnesia, silica-thoria, silica-zirconia, and various combinations of silica with these metallic oxides may also be used, such as silica-alumina-magnesia, etc. The silica and metal oxide ratios may vary over a very wide range. For example, components having a 99.8 percent silica and 0.2 percent alumina by weight at the one extreme, and percent silica-95 percent alumina at the other extreme, have been found to be quite suitable. The criterion of an acceptable active acidic metal oxide component is that it have inherent hydrocarbon cracking characteristics which are controlled when it is combined with platinum.

A variety of methods for preparing such acidic metal oxide components are known and published in the catalytic cracking and reforming arts, and since this invention is not concerned with any specific method of preparing this component of the catalyst, it is unnecessary to elaborate further on this point.

The platinum is incorporated in the active acidic metal component structure by impregnation with a platinum compound to give an amount of metal ranging between 0.05 percent and 2.5 percent by Weight of the finished catalyst. The incorporation of the platinum with the active metal oxide component may be accomplished by any of the conventional methods, such as deposition of a salt of the metal from an aqueous solution with subsequent drying and reduction of the metal compound to the metal.

Other methods of making catalysts suitable for this invention include depositing the platinum compound on a finely-divided carrier component which may be relatively inert as far as hydrocarbon cracking activity is concerned, but which has adsorption properties. Examples of such materials are alumina, freshly precipitated barium sulfate, freshly precipitated calcium sulfate, magnesium oxide, calcium oxide, titanium oxide, silica gel, calcium carbonate, activated carbon, fullers earth, kaolin, kieselguhr, diatomaceous earth, acid activated clays, bauxite and other naturally occurring sorbent clays. This finely divided carrier component upon which the platinum compound is deposited is then admixed with sufficient finely divided acidic metal oxide component, described above, so that the final catalyst contains from 25 percent to percent acidic metal oxide component. After admixing, the components are compressed into pellet form and calcined with air or reduced in hydrogen to convert the platinum compound to the metallic state.

The acidic metal oxide component may be used either in its unaltered active state or it may be used after it has had a portion of its cracking activity removed, such as by steam treatment at elevated temperatures and pressures or by treatment with a chemical poison, such as sodium or other alkali metal compounds. It is preferred, however, to employ acidic metal oxide components which have had not more than about one-half to two-thirds of their original cracking activity removed by such treatment.

specific embodiments of the invention.

EXAMPLE I An alkylated benzene fraction having the composition as set forth in Table I was passed over a platinum-silicaalumina catalyst with hydrogen in the amount of 10 moles per mole of hydrocarbon based on the average molecular weight of the alkylated benzene fraction. Experiments were made at 750 F., 850 F., and 950 F. with a pressure of pounds per square inch and a liquid hourly space velocity of 3 being employed in each experiment. The catalyst was prepared by impregnating a fresh, commercial silica-alumina cracking catalyst (approximately 12 percent alumina, 88 percent silica) with any aqueous solution of platinous tetrammino chloride in an. amount of concentration such that after drying and reducing in hydrogen at 950 F. there was deposited 0.42 percent by weight of metallic platinum based on the weight of the catalyst. The experimental results are set forth in Table I with product analysis being given on a no-loss-basis.

Since the alkylated benzene fraction of this example is so-called light detergent alkylate, i.e. the fraction too low The following examples will serve to illustrate certain in molecular weight for sulfonation' to produce commercial; detergents, these data show that such materials may be recovered by dealkylation to give high yields of henzene and valuable paraffins.

EXAMPLE II A sample of cumene (isopropyl benzene) together with hydrogen was passed over a platinum-silica-alumina cracking catalyst. The catalyst was prepared by impregnating a silica-alumina cracking catalyst (approximately 12 percent alumina, 88 percent silica) which had been treated with steam at about 1050 F. and 150 pounds per squarein'ch pressure until its cracking activity had been reduced to about 40 percent of its original activity in the fresh state, with sufiicient chloroplatinic acid solution such that upon drying and reduction the final catalyst contained 0.25 percent platinum by weight. The process conditions employed were: temperature-850 F., pressure-350 p.s.i.g., hydrogen to hydrocarbon mole ratio- 4:1, and liquid hourly space velocity-4 vol. charge per vol. of catalyst per hour. The results obtained are set forth in Table II, the product analysis being given on a no-loss basis.

Table II Products Weight percent Propane and gaseous products Benzene Alkylated benzenes in C OB molecular weight range... Cumene and n-propyl benzene Alkylated benzenes in Co molecular weight range (isomers of cumene and n-propyl benzene) Other liquid products b- DIN O0: cmwcr produced during the manufacture of synthetic detergents,

additional experiments have shown that the invention is equally applicable to alkylated benzenes and naphthalenes wherein the alkyl group contains 18 or more carbon atoms, the preferred range being, however, alkyl groups having from 3 to 20 carbon atoms. a

We claim:

1. Process for the dealkylation of alkylated aromatic hydrocarbons selected from the group consisting of monoalkylated and poly-alkylated benzenes and mono-alkylated and poly-alkylated naphthalenes wherein at least one of the alkyl groups attached to the aromatic nucleus contains at least three carbon atoms which comprises passing the hydrocarbons with excess hydrogen over a catalyst at a temperature between 600 F. and 1000 F. and' at pressures of from 50 pounds per square inch to 750 pounds per square inch, said catalyst containing as the active components a silica-containing acidic metal oxide having inherent hydrocarbon cracking activity and platinum in an amount ranging between 0.05 percent and 2.5 percent by Weight based on the weight of the finished catalyst.

2. Process for the dealkylation of alkylated aromatic hydrocarbons selected from the group consisting of monoalkylated and poly-alkylated benzenes and mono-alkylated and poly-alkylated naphthalenes wherein at least one of the alkyl groups attached to the aromatic nucleus contains at least three carbon atoms which comprises passing the hydrocarbons with excess hydrogen over a catalyst at a temperature between 750 F. and 950 F.

6 and at pressures of from 100 to 500 pounds per'squar'e inch, said catalyst containing as the active components a silica-containing acidic metal oxide having inherent hydrocarbon cracking activity and platinum in an amount ranging between 0.05 percent and 2.5 percent by weight based on the weight of the finished catalyst.

3. Process for the dealkylation of alkylated benzenes wherein at least one alkyl group attached to the benzene nucleus contains at least three carbon atoms which comprises passing the hydrocarbons with excess hydrogen over a catalyst at a temperature between 600 F. and 1000 F. and at pressures of from 50 pounds per square inch to 750 pounds per square inch, said catalyst containing as the active components a silica-containing acidic metal oxide having inherent hydrocarbon cracking activity and platinum in an amount ranging between 0.05 percent and 2.5 percent by weight based on the weight of the finished catalyst.

4. Process for the dealkylation of alkylated benzenes wherein at least one alkyl group attached to the benzene nucleus contains at least three carbon atoms which comprises passing the hydrocarbons with excess hydrogen over a catalyst at a temperature between 750 F. and 950 F. and at pressures of from 100 to 500 pounds per square inch, said catalyst containing as the active components a silica-containing acidic metal oxide having inherent hydrocarbon cracking activity and platinum in an amount ranging between 0.05 percent and 2.5 percent by weight based on the weight of the finished catalyst.

5. Process for the dealkylation of mono-alkylated benzenes produced by the alkylation of benzene with propylene polymers and wherein the alkyl group contains from 3 to 20 carbon atoms which comprises passing the hydrocarbons with excess hydrogen over a catalyst at a temperature between 600 F. and 1000 F. and at pressures of from 50 pounds per square inch to 750 pounds per square inch, said catalyst containing as the active components a silica-containing acidic metal oxide having inherent hydrocarbon cracking activity and platinum in an amount ranging between 0.05 percent and 2.5 percent by weight based on the weight of the finished catalyst.

6. The process according to claim 1 wherein the silicacontaining acidic metal oxide component of the catalyst is a silica-alumina cracking catalyst.

7. The process according to claim 2 wherein the silicacontaining acidic metal oxide component of the catalyst is a silica-alumina cracking catalyst.

8. Process for the dealkylation of alkylated aromatic hydrocarbons selected from the group consisting of monoalkylated and poly-alkylated benzenes and mono-alkylated and poly-alkylated naphthalenes wherein at least one of the alkyl groups attached to the aromatic nucleus contains at least three carbon atoms which comprises passing the hydrocarbons with excess hydrogen over a catalyst at a temperature between 600 F. and 1000 F. and at pressures of from 50 pounds per square inch to 750 pounds per square inch, said catalyst containing as the active components from 25 percent to percent of a silica-containing acidic metal oxide having inherent hydrocarbon cracking activity and platinum which has been deposited on a finely divided carrier material in an amount such that the final catalyst contains from 0.05 percent to 2.5 percent by weight of platinum.

9. Process for the dealkylation of alkylated benzenes wherein at least one alkyl group attached to the benzene nucleus contains at least three carbon atoms which comprises passing the hydrocarbons with excess hydrogen over a catalyst at a temperature between 600 F. and 1000" F. and at pressures of from 50 pounds per square inch to 750 pounds per square inch, said catalyst containing as the active components from 25 percent to 95 percent of a silica-containing acidic metal oxide having inherent hydrocarbon cracking activity and platinum which has been deposited on a finely divided carrier material in an amount such that the final catalyst contains from 0.05 percent to 2.5 percent by weight of platinum.

10. Process for the dealkylation of mono-alkylated benzenes produced by the alkylation of benzene with propylene polymers and wherein the alkyl group contains from 3 to 20 carbon atoms which comprises passing the hydrocarbons with excess hydrogen over a catalyst at a temperature between 600 F. and 1000 F. and at pressures of from 50 pounds per square inch to 750 pounds per square inch, said catalyst containing as the active components from 25 percent to 95 percent of a silicacontaining acidic metal oxide having inherent hydrocarbon cracking activity and platinum which has been deposited on afinely divided carrier material in an amount such that the final catalyst contains from 0.05 percent to 2.5 percent by weight of platinum.

References Cited in the file of this patent UNITED STATES PATENTS 2,692,293 Heinemann Oct. 19, 1954 2,709,194 Clough May 24, 1955 2,801,271 Schlatter July 30, 157

FOREIGN PATENTS 712,980 Great Britain Aug. 4, 1954 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 233M842 April 5 1960 Paul M0 Pitts Jr, 0 et 6116 It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line Z2 for "occuring" read occurring column 4, line 55 for "amount of read amount and same column 4 Table I column l line l thereef for "Parafins" read Paraffins same column 4 same Table I under the heading "Products" third column thereof second item for 9802" read 98.,1 column 8 line 9 list of References Cited under UNITED STATES PATENTS the third reference date for "July 30 157 read July 3O 1957 a Signed and sealed this 6th day of September 19600 (SEAL) Attest:

ERNEST W, SWIDER ROBERT C. WATSON Attesting Oflicer Commissioner of Patents 

1. PROCESS FOR THE DEALKYLATION OF ALKYLATED AROMATIC HYDROCARBONS SELECTED FROM THE GROUP CONSISTING OF MONOALKYLATED AND POLY-ALKYLATED BENZENES AND MONO-ALKYLATED AND POLY-ALKYLATED NAPHTHALENES WHEREIN AT LEAST ONE OF THE ALKYL GROUPS ATTACHED TO THE AROMATIC NUCLEUS CONTAINS AT LEAST THREE CARBON ATOMS WHICH COMPRISES PASSING THE HYDROCARBONS WITH EXCESS HYDROGEN OVER A CATALYST AT A TEMPERTURE BETWEEN 600*F. AND 1000*F. AND AT PRESSURES OF FROM 50 POUNDS PER SQUARE INCH TO 750 POUNDS PER SQUARE INCH, SAID CATALYST CONTAINING AS THE ACTIVE COMPONENTS A SILICA-CONTAINING ACIDIC METAL OXIDE HAVING INHERENT HYDROCARBON CRACKING ACTIVITY AND PLATINUM IN AN AMOUNT RANGING BETWEEN 0.05 PERCENT AND 2.5 PERCENT BY WEIGHT BASED ON THE WEIGHT OF THE FINISHED CATALYST. 